Fracturing of rocks by passing pulses of current between electrodes within a formation is discussed, for example, by Melton and Cross, Quarterly, Colorado School of Mines (Jul. 1967), 62, No. 3, 45-60, (“Melton”) which discusses passing short, high energy electrical pulses through Green River Oil Shale to create horizontal permeable paths for subsequent fire flooding to heat the oil shale and produce hydrocarbons by thermal cracking of kerogen. Field tests were disclosed wherein high voltage pulses of electricity created zones of increased permeability between wellbores that were up to 115 feet apart.
Hydraulic fracturing is typically utilized to enhance production from formations which have low permeabilities. The hydraulic fractures are propped open by proppants such as sand having specific distribution of sizes. By providing hydraulic fractures, a considerably larger surface area is provided for hydrocarbons to migrate to through the low permeability formation. Improvements to hydraulic fracturing technology has permitted profitable production of natural gas and light hydrocarbon liquids from formations previously thought to be impractical to produce. Although hydraulic fracturing has enabled economical production from many low permeability formations, hydraulic fractures cause increases in formation stress due to compression of the formation to create volume for the fractures. This increased stress results in reduction of formation permeability. Further, providing hydraulic fractures can be a relatively high portion of the total costs of drilling and completing a well and requires pumping into the formation and subsequently removing from the formation large volumes of water.
Novas Energy Services, located at Moscow, Kievskoe Highway, Business Center “Rumyantsevo”, building “G”, offers services for oil field production and injection wells that includes utilization of plasma-pulse action in the wells to improve the well drained zone permeability. It is claimed that this treatment increases oil flow rates into the well and injectivity from injection wells. Electrical pulses of three thousand to five thousand volts lasting from fifty to fifty three microseconds are applied releasing considerable amounts of energy creating shock waves. The resonance vibrations created in the productive stratum are said to make it possible to clean the existing filtration channels and create new filtration channels at distances of over fifteen hundred meters from the well being treated. The plasma pulses created by Novas Energy Services appear to be utilized to generate mechanical shock waves that are intended to open existing pores within the formation. Because the release of the electrical pulses within the wellbore are directed toward electrical grounds, the current density decreases rapidly with distance from the wellbore thus the mechanism of Novas Energy Services is not to remove mass from the formation by vaporization of mineral mass.
Electric rock breaking is discussed in B. S. Harper, “Nederburt Nimer”, The Southern African Institute of Mining and Metallurgy, Narrow Vein and Reef 2008. Electric plasma arcs are considered for the purpose of removing rocks for following small veins of gold ore. Placement of electrodes within hydraulic fractures in a formation is known, for example, from U.S. Pat. No. 7,631,691. In this patent, electrical voltage is applied across the fracture to provide heat to the formation for pyrolysis of kerogen within the formation.